Reinforced concrete structures, particularly in northern and coastal states, may commonly be exposed to chlorides either from de-icing salts and/or seawater. Chloride-induced corrosion has been considered a major cause of premature failure of such structures. Chloride-induced corrosion affects the reinforcing structure of the concrete, such as rebar, grids or plates that may be used in the concrete structure. The chloride ions may cause the passivating layer that forms on the reinforcing structure to become permeable allowing for further oxidation and corrosion of the reinforcing structure. In addition, the character of the concrete material may be affected, wherein an acidic environment may develop and remove the passivating layer that forms on the reinforcing structure. The corrosion products may exhibit a volume greater than the initial volume of the original reinforcing structure, which may eventually cause cracking and spallation of the concrete due to expansion caused by the corrosion products.
As reinforced concrete is used in many infrastructure projects, such as bridges and highways, monitoring the corrosion of these structures may be of relative significance. For example, the National Highway Bridges Reconstruction and Inspection Act passed Jul. 25, 2008 mandates annual inspections of structurally deficient highway bridges. Parameters of interest include not only concentration of chloride but also, other deleterious ion species and the character of the concrete material itself.